Construction machine

ABSTRACT

An efficient and quiet construction machine has a heat exchanger in which the air flowing out from an axial flow fan avoids collision with the engine. The axial flow fan includes a plurality of blade pieces, a fan ring which guides a flow of air to the axial flow fan, a heat exchanger which is disposed on an upstream side or a downstream side of the flow of air with respect to the axial flow fan, and a structure which is disposed on the downstream side of the flow of air with respect to the axial flow fan. The fan ring includes a suction-side rounded part which reduces a flow channel on a suction side and a discharge-side rounded part which expands the flow channel on a discharge side, and each of the blade pieces is inclined at a sweep forward angle from an axial center toward a rotation direction.

TECHNICAL FIELD

The present invention relates to a construction machine provided with a cooling system for supplying cooling air to a heat exchanger such as a radiator by means of an axial flow fan.

BACKGROUND ART

Generally, in a construction machine such as a hydraulic excavator, a hydraulic pump is driven by a diesel engine so that hydraulic energy of the hydraulic pump can be used for excavation work, travelling and so on. To that end, heat exchangers such as a radiator for cooling the engine and an oil cooler for cooling hydraulic oil, and a cooling fan for supplying cooling air to these heat exchangers are disposed together with the engine and the hydraulic pump inside an engine room.

For example, Patent Literature 1 has been known as a background-art technique in this technical field. An example in which a heat exchanger for a construction machine is cooled by means of an inexpensive thin axial flow fan has been disclosed in this Patent Literature 1. This example has a configuration in which the axial flow fan is rotated by power transmitted from a crank shaft of the engine through a pulley and a fan belt. The heat exchanger is often disposed on an upstream side of the axial flow fan. After the air flowing in from the outside through suction ports passes through the heat exchanger, the air is guided to the axial flow fan by a fan shroud and a fan ring. The air pressurized by the axial flow fan flows around the engine (structure) and is then released to the outside through an exhaust port.

In recent years, air-cooling intercoolers or water-cooling EGR (Exhaust Gas Recirculation) devices have been mounted on construction machines as units for reducing exhaust gas in order to respond to the regulation of exhaust gas of diesel engines mounted on the construction machines. In addition, common rails have been mounted to control the timing of fuel injection to thereby suppress emission of exhaust gas.

CITATION LIST Patent Literature

-   Patent Literature 1: JP-A-2010-270670

SUMMARY OF INVENTION Technical Problem

For the aforementioned exhaust gas emission control, a heat exchanger that is an intercooler is newly added to a radiator and an oil cooler which have been mounted heretofore. It is also necessary to enhance the heat radiation performance of the radiator to further cool the water-cooling EGR device. Thus, the flow rate of air required for cooling has increased in recent construction machines.

In addition, a heat exchanger has been increasing in size correspondingly to the increase in cooling load. However, the number of devices mounted in a limited space within an engine room has been increased. Thus, there is a limit to the increase in the size of the heat exchanger. In the case of a machine where the frontal area of a heat exchanger cannot be enlarged anymore, the size of the heat exchanger may be increased to increase the thickness of the heat exchanger.

When the frontal area of the heat exchanger is enlarged, the heat exchanger however becomes large relatively to a fan. Since an end portion of the heat exchanger has a distance from the fan, cooling air hardly flow in that portion. It is therefore difficult to sufficiently exert the effect of the increasing size of the heat exchanger. The increase in the diameter of the fan corresponding to the heat exchanger may be considered if the space allows. However, the increase in power for driving the fan gives restriction to power which can be used as the construction machine.

On the other hand, when the size of the heat exchanger is increased to increase the thickness of the heat exchanger, the space in the direction of a rotary shaft of the fan needs to be narrowed correspondingly. When the distance between the heat exchanger and the fan is reduced correspondingly, the wind speed distribution of the air passing through the heat exchanger may deteriorate. When the distance between the fan and the engine is reduced, the flow flowing out from the fan may collide with the engine easily to thereby increase the loss of pressure in a flow channel of the cooling air. Thus, the rotation speed of the fan required for obtaining the required flow rate of the air increases. As a result, the shaft power of the fan or the noise increases, and hence the noise of the construction machine increases and the fuel consumption deteriorates.

Further, in the case of the construction machine, suction of the cooling air due to travelling wind as in a car cannot be expected. Therefore, all the required flow rate of the cooling air must be sucked by the fan. Accordingly, the rotation speed of the fan must be set to be higher than in a car, so that the shaft power of the fan or the noise may be increased easily. This also affects the fuel consumption or the noise of the construction machine as a whole.

The invention has been accomplished in consideration of the aforementioned actual circumstances. An object of the invention is to provide a highly efficient and quiet construction machine in which the wind speed distribution in a heat exchanger is excellent so that the air flowing out from an axial flow fan can avoid collision with an engine.

Solution to Problem

In order to solve the foregoing problems, the invention provides a construction machine including: an axial flow fan which includes a plurality of blade pieces and rotates around an axis; a fan ring which is disposed around the axial flow fan and guides a flow of air to the axial flow fan; a heat exchanger which is disposed on an upstream side or a downstream side of the flow of air with respect to the axial flow fan; and a structure which is disposed on the downstream side of the flow of air with respect to the axial flow fan; wherein: the fan ring includes a suction-side rounded part which reduces a flow channel on a suction side and a discharge-side rounded part which expands the flow channel on a discharge side; each of the blade pieces is formed with a leading edge, a trailing edge and a tip, inclined at a sweep forward angle θ from an axial center toward a rotation direction, and attached in a posture in which the blade piece slants forward on the suction side; and in a state in which the axial flow fan is attached to an inner side of the fan ring, a first intersection where the trailing edge of each of the blade pieces intersects the tip of the same is located within a width range of the discharge-side rounded part.

According to the invention configured thus, a centripetal flow can be formed on the suction side of the axial flow fan, and a centrifugal flow can be formed on the discharge side of the same. Thus, cooling air can be made to flow with a good wind speed distribution up to an end portion of a large-sized heat exchanger disposed on the upstream side or the downstream side of the flow of the air with respect to the axial flow fan. In addition, the air flowing out from the axial flow fan can avoid collision with a structure such as an engine located on the downstream side. It is therefore possible to prevent the loss of pressure from increasing in the flow channel of the cooling air.

According to the invention, the heat radiation performance in the heat exchanger can be improved and the hot air around the engine can be ventilated efficiently. Accordingly, the occurrence of overheat in the engine or hydraulic oil can be suppressed. Further, when the heat radiation performance in the heat exchanger is improved and the loss of pressure in the flow channel of the cooling air is reduced, the flow rate required for cooling can be reduced. Accordingly, the rotation speed of the axial flow fan can be suppressed. This can also contribute to suppression of noise, improvement of fuel consumption achieved by reduction in driving power, and so on.

In addition, in the aforementioned configuration, it is preferable that the sweep forward angle θ is within a range not smaller than 5° and not larger than 25°. With this configuration, even when the rotation speed of the axial flow fan is increased to obtain a design flow rate (100% Q), the increase in noise generated at that time can be suppressed to a level (that is, +3 dB or lower) that cannot be sensed by any person. In addition, even when the loss of pressure increases because the cooling air receives resistance of the structure which is located on the discharge side of the cooling air, reduction of the flow rate can be prevented from falling below an allowable lower limit value (that is, −10%).

In addition, in the aforementioned configuration, it is preferable that a second intersection where the leading edge of each of the blade pieces intersects the tip of the same is located to protrude from the suction-side rounded part toward the upstream side of the flow of air. With this configuration, the centripetal flow on the suction side of the axial flow fan and the centrifugal flow on the discharge side of the same can be made smoother. Accordingly, the heat radiation performance of the heat exchanger can be further improved.

Advantageous Effects of Invention

According to the invention, it is possible to provide a highly efficient and quiet construction machine in which the wind speed distribution in a heat exchanger is kept so excellent that the air flowing out from an axial flow fan can avoid collision with an engine.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] An external perspective view of a hydraulic excavator according to a first example of the invention.

[FIG. 2] A side sectional view of an engine room of the hydraulic excavator shown in FIG. 1.

[FIG. 3] An enlarged side view of main parts of an axial flow fan and a fan ring shown in FIG. 2.

[FIG. 4] An enlarged plan view of the main part of the axial flow fan shown in FIG. 2.

[FIG. 5] A graph showing the relationship between a sweep forward angle of each blade of the axial flow fan shown in FIG. 2 and relative noise.

[FIG. 6] A graph showing the relationship between the sweep forward angle of each blade of the axial flow fan shown in FIG. 2 and a change of the flow rate of air at the time of the increase in loss of pressure.

[FIG. 7] A side sectional view of an engine room of a hydraulic excavator according to a second example of the invention.

DESCRIPTION OF EMBODIMENTS

A hydraulic excavator which is an embodiment of a construction machine according to the invention will be described below with reference to the drawings. As shown in FIG. 1, the hydraulic excavator according to a first example is provided with a crawler 24, an upper rotary body 26 which is disposed on the crawler 24, a front work machine which is attached to the upper rotary body 26 so that the front work machine can rotate vertically to perform excavation work and so on, and a cab 25 which is an operation room. The front work machine is provided with a boom 21 which is attached to the upper rotary body 26 so that the boom 21 can be depressed and elevated, an arm 22 which is rotatably attached to a front end of the boom 21, a bucket 23 which is rotatably attached to a front end of the arm 22, and hydraulic cylinders which drive these parts. In addition, the upper rotary body 26 includes an engine room 10 at the rear thereof. The reference numeral 27 represents a counterweight 27.

As shown in FIG. 2, an axial flow fan 2, a fan ring 3 which guides a flow of air to the axial flow fan 2, a heat exchanger 1, an engine (structure) 4, and a battery 9 are placed in the engine room 10. In addition, suction ports 7 which serve as inlets/outlets of the air are provided in an upper portion of the engine room 10, and exhaust ports 8 are provided in the upper portion and a lower portion of the engine room 10. As for the positional relation among the heat exchanger 1, the axial flow fan 2 and the engine 4, the heat exchanger 1 is located on an upstream side of the flow of air with respect to the axial flow fan 2, and the engine 4 is located on a downstream side of the flow of air with respect to the axial flow fan 2. As a result of the positional relation, the axial flow fan 2 is requested to form a centripetal flow flowing toward the center of the fan on the upstream side, and requested to form a centrifugal flow flowing in the centrifugal direction of the fan on the downstream side. To that end, forward-swept/forward-slanting blades are used in this example (as will be described in detail later).

The heat exchanger 1 is constituted by a radiator, an oil cooler and an intercooler, and those devices are disposed in parallel. In recent years, the heat exchanger 1 tends to increase in size in order to enhance the cooling capacity. Also in this example, the entire external shape of the heat exchanger 1 is larger than that of the axial flow fan 2.

The engine 4 is provided with a crank shaft (output shaft) 4 a. Power for rotating the axial flow fan 2 is transmitted from the crank shaft 4 a through a pulley 5 and a fan belt 6. The fan 2 is rotated with a rotation speed adjusted properly by the pulley 5.

Next, the axial flow fan 2 and the fan ring 3 will be described in detail. The axial flow fan 2 is constituted by a columnar hub 2 b which is attached to a rotary shaft 2 c, and a plurality of blades (blade pieces) 2 a which are provided around the hub 2 b, as shown in FIG. 2. In addition, the fan ring 3 formed into an annular shape is provided around the axial flow fan 2 and provided with a suction-side rounded part 3 a having a curved surface on the suction side of the axial flow fan 2 and a discharge-side rounded part 3 b having a curved surface on the discharge side of the same, as shown in FIG. 2 and FIG. 3. That is, in the fan ring 3, both the suction-side side edge portion and the discharge-side side edge portion are formed into rounded shapes respectively.

Each blade 2 a is formed to have a leading edge 2 g, a tip 2 e and a trailing edge 2 d as shown in FIG. 3. In a state in which the axial flow fan 2 is attached to an inner side of the fan ring 3, a second intersection Q where the leading edge 2 g intersects the tip 2 e protrudes from the suction-side rounded part 3 a of the fan ring 3 and on the upstream side (suction side) by a length L, and a first intersection P where the trailing edge 2 d intersects the tip 2 e is located within a range of a width W of the discharge-side rounded part 3 b of the fan ring 3.

Further, the shape of each blade 2 a will be described in detail. As shown in FIG. 3, the blade 2 a protrudes on the suction side in a position where the diameter thereof is larger. Thus, the blade 2 a is inclined (slanting forward) as a whole. In addition, as shown in FIG. 4, the blade 2 a protrudes (is swept forward) in the rotation direction in a site where the radial position thereof is larger. The sweep forward angle is θ. That is, each blade 2 a of the axial flow fan 2 used in this example is a forward-swept/forward-slanting blade. The sweep forward angle θ mentioned herein is an angle indicating how the trailing edge 2 d of the blade 2 a protrudes in the rotation direction. Specifically, the sweep forward angle θ corresponds to an internal angle A of a triangle AOP formed by connecting a center point A of the rotary shaft 2 c, a third intersection O where the trailing edge 2 d of the blade 2 a intersects the hub 2 b, and the first intersection P.

Next, the flow of the air made by the axial flow fan 2 will be described. Each arrow in FIG. 2 and FIG. 3 shows the flow of the air. Generally, an axial flow fan with forward-swept/forward-slanting blades is characterized in that a centripetal flow flowing toward the rotation center of the fan is formed on the upstream side (suction side) of the fan so that the fan can also suck the air from the lateral side of the fan partially. Thus, when the axial flow fan 2 rotates, a flow of the air is induced due to a difference in pressure occurring between before and behind the axial flow fan 2. First, the low-temperature air outside the engine room 10 flows into the engine room 10 through the suction ports 7. When passing through the heat exchanger 1, the air takes heat away from fluid (such as engine cooling water, hydraulic oil, compressed air, etc.) inside tubes of the heat exchanger 1, and the temperature of the air itself becomes high. After that, the air flows into the axial flow fan 2 to be thereby increased in pressure, and then flows out from the axial flow fan 2. The air flows around the engine 4, and is then released to the outside of the engine room 10 from the exhaust ports 8. Due to the flow generated thus, it is possible to make a flow of the air reaching up to the end portion of the heat exchanger 1 even if the heat exchanger 1 is larger than the axial flow fan 2. It is therefore possible to achieve heat exchange with high efficiency.

On the other hand, the axial flow fan with forward-swept/forward-slanting blades is characterized in that the air easily flows out in the axial flow direction along the rotary shaft 2 c on the downstream side (discharge side) of the fan. Therefore, there is a possibility that the air flowing out from the axial flow fan 2 may directly collide with the engine 4 to thereby increase the loss of pressure.

In the case of this example, therefore, the first intersection P where the trailing edge 2 d intersects the tip 2 e is located within the range of the width W of the discharge-side rounded part 3 b of the fan ring 3, as shown in FIG. 3. In this manner, the air flowing out from the axial flow fan 2 flows along the discharge-side rounded part 3 b of the fan ring 3 due to the Coanda effect, so that the flow of the air can flow in the radial direction easily to be a centrifugal flow. As a result, the air flowing out from the axial flow fan 2 can avoid collision with the engine 4, so that the increase in loss of pressure can be suppressed. In addition, since the discharge-side rounded part 3 b of the fan ring 3 also serves as a diffuser, it is also possible to expect an effect that a flow flowing out with a high absolute velocity and from the first intersection P located at a rear end of each blade 2 a is reduced in velocity effectively to increase the static pressure.

As understood from the above description, in the hydraulic excavator according to this example, effective heat exchange can be achieved by a good wind speed distribution in the heat exchanger 1, and the air flowing out can be prevented from colliding with the engine 4 on the downstream side of the axial flow fan 2. Thus, it is possible to attain a flow channel configuration with a low loss of pressure.

On the other hand, in the hydraulic excavator, noise of the axial flow fan 2 or the engine 4 leaks from opening portions (the suction ports 7 and the exhaust ports 8) so as to increase ambient noise. Therefore, there is a need to provide the opening portions, if possible, in an upper surface or a lower surface of the engine room 10 so as to prevent fan noise or engine noise from being transmitted directly to any person around the hydraulic excavator. With respect to this point, in the configuration of this example, inflow (centripetal flow) from the radial direction of the axial flow fan 2 and outflow (centrifugal flow) to the radial direction are made compatible. It is therefore favorable to provide the opening portions in the upper portion of the engine room 10 laterally in view from the rotary shaft 2 c of the axial flow fan 2. It is also possible to contribute to reduction of noise in the hydraulic excavator as a whole while suppressing the total loss of pressure.

When the sweep forward angle θ is made too large, the centripetal flow on the suction side of the axial flow fan 2 and further the axial flow on the discharge side of the same are enhanced so that it is difficult to form the centrifugal flow on the downstream side in spite of the aforementioned configuration. In addition, according to the value of the sweep forward angle A, the value of the fan noise may vary and the flow rate may be also affected. Therefore, in order to obtain a preferable angle range of the sweep forward angle θ, the present inventors performed simulation analysis as follows.

First, the present inventors performed simulation analysis about noise when a design flow rate (100% Q) was attained. For example, when the static pressure of the axial flow fan 2 is low, the rotation speed of the fan needs to be increased to obtain a design flow rate (100% Q) required for cooling. Increase in rotation speed for attaining the design flow rate can be converted into a change in noise as shown in FIG. 5. FIG. 5 shows the change in noise with reference to the sweep forward angle θ=0°. The sweep forward angle θ is desired to be designed to attain the lowest noise (that is, near θ=0°) if possible. However, it is said that noise increase of 3 dB (twice sound energy) corresponds to a level difference that can be recognized as noise increase by human ears. It is therefore possible to allow noise increase not larger than this level. From this point of view, it can be considered that substantially the lowest level as noise that can be sensed by any person can be attained if the sweep forward angle θ is set to be not larger than about 25°. That is, it has been found out from this simulation analysis that the upper limit of the sweep forward angle θ with which noise can be suppressed to be not larger than +3 dB is 25°.

Next, the present inventors performed simulation analysis about the reduction of the flow rate when the loss of pressure (resistance in a flow channel) increased by 30% relatively to that at the time of design. The result of the simulation analysis is shown in FIG. 6. Due to the environment in which a construction machine is operating, rubbish, soil, etc. are deposited on a heat exchanger. That is, an axial flow fan is operating under such an environment that the resistance in the flow channel increases gradually. Practically, after operation for a certain time, the heat exchanger or a filter is cleaned to remove clogging so as to suppress the increase of the resistance in the flow channel. In view of user-friendliness, it is desired to make the interval of the cleaning as long as possible. In other words, it is desired to use an axial flow fan in which the reduction of the flow rate can be kept as small as possible even if the resistance in the flow channel increases. To this end, it is desirable from FIG. 6 that the sweep forward angle θ is not smaller than about 5° and not larger than about 40° when 10% as the reduction of the flow rate is the allowable lower limit.

From the aforementioned results of the simulation analysis, it has been found out that the sweep forward angle θ serving as a threshold satisfying both the design requests is not smaller than 5° and not larger than 25°. Therefore, the sweep forward angle θ of each blade 2 a is set to be not smaller than 5° and not larger than 25° in the axial flow fan 2 according to the example.

Next, a second example of the invention will be described with reference to FIG. 7. FIG. 7 shows a side sectional view of an engine room in a hydraulic excavator according to the second example. In the second example, constituents the same as those in the first example are referred to by the same numerals correspondingly, and description thereof will be omitted.

In this example, an axial flow fan 2 is placed separately from an engine 4. A heat exchanger 1 is disposed on a downstream side of the axial flow fan 2. Suction ports 7 are disposed in upper and lower wall surfaces of an engine room 10 on an upstream side of the axial flow fan 2, particularly in the side surfaces in view from a rotary shaft 2 c of the axial flow fan 2. The axial flow fan 2 is connected directly to a hydraulic motor 11 and driven thereby. A fan ring 3 is placed around the axial flow fan 2 in the same manner as in the first example.

When the axial flow fan 2 rotates, the air flows into the engine room 10 through the suction ports 7. The air which has passed through the axial flow fan 2 undergoes heat exchange in the heat exchanger 1. Then, the air is discharged to the outside through upper and lower exhaust ports 8 on the downstream side.

Also in the configuration of the second example, a centripetal flow on the upstream side of the axial flow fan 2 and a centrifugal flow on the downstream side of the same are made compatible. Thus, the air can flow in smoothly through the suction ports 7 provided laterally in view from the rotary shaft 2 c. In addition, when the flow flowing out from the axial flow fan 2 enters the heat exchanger 1, the air also enters the end portion of the heat exchanger 1. Thus, effective heat exchanger can be attained. Since the suction ports 7 and the exhaust ports 8 are provided in the upper surface and the lower surface of the engine room 10, noise from the axial flow fan 2 or the motor 11 can be prevented from reaching ears of any person around the hydraulic excavator. Thus, it is possible to contribute to reduction in noise around the hydraulic excavator.

Although the effect of the invention has been described along the aforementioned examples, the invention is not always limited thereto. In the invention, for example, any method or any kind can be used as the method for driving the fan or the kind of the heat exchanger. The effect of the invention can be also expected in another construction machine than the hydraulic excavator.

REFERENCE SIGNS LIST

-   1 heat exchanger -   2 axial flow fan -   2 a blade (blade piece) -   2 c rotary shaft (axis) -   2 d trailing edge -   2 e tip -   2 g leading edge

3 fan ring

3 a suction-side rounded part

3 b discharge-side rounded part

4 engine (structure)

P first intersection

Q second intersection

W width of discharge-side rounded part

θ sweep forward angle 

1. A construction machine comprising: an axial flow fan which includes a plurality of blade pieces and rotates around an axis; a fan ring which is disposed around the axial flow fan and guides a flow of air to the axial flow fan; a heat exchanger which is disposed on an upstream side or a downstream side of the flow of air with respect to the axial flow fan; and a structure which is disposed on the downstream side of the flow of air with respect to the axial flow fan; wherein: the fan ring includes a suction-side rounded part which reduces a flow channel on a suction side and a discharge-side rounded part which expands the flow channel on a discharge side; each of the blade pieces is formed with a leading edge, a trailing edge and a tip, inclined at a sweep forward angle θ from an axial center toward a rotation direction, and attached in a posture in which the blade piece slants forward on the suction side; and in a state in which the axial flow fan is attached to an inner side of the fan ring, a first intersection where the trailing edge of each of the blade pieces intersects the tip of the same is located within a width range of the discharge-side rounded part; the sweep forward angle θ is within a range not smaller than 5° and not larger than 25°; and a second intersection where the leading edge of each of the blade pieces intersects the tip of the same is located to protrude from the suction-side rounded part toward the upstream side of the flow or air, so that; the air forms a centripetal flow on the upstream side of the axial flow fan, and forms a centrifugal flow on the downstream side of the same to thereby avoid collision with the structure.
 2. A construction machine according to claim 1, wherein: the plurality of blade pieces are disposed around a columnar hub attached to a rotary shaft of the axial flow fan; the sweep forward angle θ is defined as an internal angle A of a triangle AOP formed by connecting points A, O and P, where the point A designates a center point of the rotary shaft of the axial flow fan, the point O designates a third intersection where the trailing edge of the blade piece intersects the hub, and the point P designates the first intersection; and the internal angle A is within a range not smaller than 5° and not larger than 25°.
 3. (canceled) 